PROVO — It’ll be Senior Day Saturday at LaVell Edwards Stadium, but, in many respects, 2017 has been the Year of the Underclassmen at BYU.

Whether it's been due to talent that couldn’t be restrained or a plethora of injuries (37 different players have missed games) that opened opportunities, a host of freshmen and sophomores have seen significant playing time for the Cougars.

It’s a youth movement of sorts at BYU.

In the short run, learning on the job can be tough in terms of wins and losses. But, in the long run, the experience that players are getting can be a boon the future of a program.

“We’ve been hit in a lot of different positions (with injuries), but it’s been great for the young guys to step up, and guys that weren’t planning to get a lot of reps are getting a lot of valuable experience that we can utilize for this team next year,” said coach Kalani Sitake.

Take the quarterback position. With two games remaining, the starter, Joe Critchlow, and his backup, Kody Wilstead, are true freshmen fresh off missions.

Critchlow won his first start last Friday against UNLV, and his 64 percent completion rate ranks no. 1 among the five true freshmen QBs that started their first game at BYU — Tanner Mangum (61 percent), Taysom Hill (57 percent), Jake Heaps (53 percent), Drew Miller (53 percent).

“Ty did a great job preparing him (Critchlow) for this moment. Ty’s been there before,” Sitake said. “For a young guy like that without a lot of experience, on the road, especially with the offense having so many issues, it was nice to have him perform well. Not perfect, but well enough to rely on our run game and for him to make the throws when he needed to.”

Meanwhile, Matt Bushman has already set a school record for freshman tight end receptions with 45. The previous mark was set by Dan Coats, who had 30 catches in 2003.

Up until he was sidelined after off-field issues a few weeks ago, freshman Ula Tolutau was BYU’s leading rusher (he’s gained 303 yards and scored two touchdowns).

Consider that there is a sophomore starting at left tackle, Thomas Shoaf, and there are four freshmen backing up the five starters on the offense line — Chandon Herring, Austin Chambers, James Empey and Kieffer Longson. The other backup is sophomore Addison Pulsipher.

On the defensive side of the ball, freshman Khyiris Tonga has made his presence felt with 3.5 tackles-for-loss and 1.5 sacks.

“Someone said, ‘Maybe we have another Haloti Ngata (who starred at Oregon and is in his 12th season in the NFL) in the making.’ He has that talent and potential,” said linebackers coach Steve Kaufusi. “The heart part, the will, the passion, those are the things that come along with his abilities. He has that. It would have been easy to redshirt him because he was just off a mission. But we needed him. He’s more stout than everybody else. There are fundamental things to work on but he has that little thing you look for. Anybody can coach a blue chip guy, right? He’s a guy I’m excited about. He’ll be a load next year.”

Having recently returned home from a mission, Tonga didn’t plan on playing this season.

“I thought I’d wait a year and try to get in shape. I just jumped right into it,” he said. “I’ve got a long way to go to get back into playing shape. It’s been a huge learning process. It’s been amazing to be able to play with guys like Fred (Warner), Butch (Pau’u), Corbin (Kaufusi) and Sione (Takitaki).”

Senior defensive lineman Handsome Tanielu said Tonga is only one of many young defensive players who will be a force in upcoming seasons.

“There are some other kids that you guys don’t know about that are behind the scenes right now that are real freshmen, not returned missionary freshmen,” Tanielu said. “They’ll grow and be just as good as Khyiris — Keanu Saleapaga, Earl Mariner, Wayne Tei-Kirby, Lorenzo Fauatea. Those are freshmen D-linemen that will contribute in the coming years. I’m excited for the future. The D-line will dominate next year.”

In addition to the freshmen, a bunch of sophomores have played a lot or have had big roles this season, including quarterback Beau Hoge (who has suffered a season-ending injury); running backs KJ Hall and Austin Kafentzis; wide receivers Micah Simon, Aleva Hifo and Talon Shumway; defensive lineman Trajan Pili; linebacker Johnny Tapusoa; and cornerbacks Troy Warner (who started eight games before his injury), Dayan Ghanwoloku and Chris Wilcox.

Right now, the face of the BYU offense is a freshman, just months removed from a mission.

“It’s cool to see guys like Joe Critchlow come in as a freshman and running the offense," Tonga said. "We have a lot of young talent on the field right now, and a lot of guys are redshirting that will play next year.”